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tec CONSTRUCTION AND MANUFACTURE OF
£ AUTOMOBILES
BY RALPTI E Fr ANDERS SECCivD
MACHINERY'S REFERENCE «QT.vRlEb-
PUBLISHED bY MAC TINLRY, NEW YORK
MACHINERY'S REFERENCE SERIES
EACH NUMBER IS A UNIT IN A SERIES ON ELECTRICAL AND
STEAM ENGINEERING DRAWING AND MACHINE
DESIGN AND SHOP PRACTICE
NUMBER 60
CONSTRUCTION
AND MANUFACTURE OF
AUTOMOBILES
By RALPH E. FLANDERS SECOND EDITION
CONTENTS
Design and Construction of a High-grade Motor Car - 3 Automobile Manufacturing Methods - 18
Manufacturing Equalizing Gears 31
Copyright, 1912, The Industrial Press, Publishers of MACHINERY. 49-55 Lafayette Street, New York City
CHAPTER I
DESIGN AND CONSTRUCTION OP A HIGH-GRADE MOTOR CAR*
The following description of a 40 H. P. automobile, built by tuc Stevens-Duryea Company, of Chicopee Falls, Mass., may, except for certain important details which will be specifically mentioned, be taken as typical of the design of high-grade cars in general. In Fig. 1 is shown a side view of the "Model Y," 40 horsepower, six-cylinder machine, with 36-inch wheels and 142-inch wheel-base. An automobile may be divided into two parts— the body and the "chassis." The former is the product of the carriage-maker's art, the latter of the mechanic's
Fig. I. Stevena-Duryea "Big Six" Motor Car, 191O Model
and engineer's. The chassis of this machine is shown in Figs. 2 and 3, to which reference will now be made.
The mechanism and body of the car are supported by a frame whose side members, of chrome-nickel steel, are shown at A. These are connected by four cross pieces, and are supported on the front and rear axles by the spring connections shown. The cross pieces are also pressed from chrome-nickel steel, and are hydraulically riveted to the side frames. A platform spring suspension is used at the rear, hung on connecting shackles designed to overcome the side roll met
* MACHINERY, October, 1909.
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DESIGN OF A HIGH-GRADE MOTOR CAR
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No. 60— AUTOMOBILE CONSTRUCTION
available horsepower per hundredweight of load. It also permits the power plant to be assembled as a whole and to be bolted in place with- out fitting. This construction, which is the distinctive point in the design of this motor, has been successfully followed by the builders for the last five years, and it is one of the things which serve to give an attractive mechanical appearance to the whole mechanism. Only one double set of universal joints is required, that connecting the propeller shaft with the transmission gearing at one end, and the differential gearing at the other.
The cylinders are grouped in three two-cylinder castings C, bolted to the crank case N. As is common with internal combustion engines in ordinary practice, they are water jacketed, there being a continuous
DESIGN OF A HIGH-GRADE MOTOR CAR
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No, 60— AUTOMOBILE CONSTRUCTION
at the forward end of the erank-shatt, as here shown, is unusual, the common construction being to locate it between the crank-shaft and the clutch. It tends, in particular, to bring more of the weight onto the front wheels, off from the heavily loaded rear wheels of the ma- chine, and permits the reducing of the clearance over the roadbed in ib* center of the chassis, where there is the greatest danger of strik- ing on high water-bars, railroad crossings, etc. It will be readily «een that more clearance is required at the center of the machine than at the axles, when crossing a hump in the road.
Lubrication, Ignition, etc.
Two shafts mounted in the crank casing, one on each side, above and parallel to the crank-shaft, are driven from it by enclosed gearing.
Fig. 6. View of Engine from Beneath, showing Removal of Piston, Cam- and Lay-shafts, etc., without Dismantling
The one at the side shown in Fig. 5 is the cam-shaft and is provided with twelve sets of cams for operating the six inlet and six exhaust valves, whose stems and closing springs are plainly shown in the engraving. The driving gear of this cam-shaft is also connected with a pinion on the armature shaft of the magneto, whose function will be described later. The shaft on that side of the machine shown in Fig. 4, is known as the lay-shaft. Its office is the driving of the timer Y, which controls the ignition, the driving of the forced lubrication mechanism at W, and of the water jacket circulation pump 0.
The lubricator gives a forced oil supply with sight feed, and is always in operation when the engine is in motion. The six-throw crank-shaft is mounted in four bearings in the crank case, with two cranks between each pair of bearings. The boxes at these points are connected with the lubricator W. The lower half of the crank case forms a reservoir for the oil escaping from the main bearings. The connecting-rod splashes into this and thus supplies the pistons, con- necting-rod bearings, etc., with the necessary lubrication.
DESIGN OF A HIGH-GRADE MOTOR CAR
The ignition in each cylinder is effected by either of two systems, the one by storage or dry battery and induction coil, and the other by means of a magneto U connected by gearing with the crank-shaft. The battery and spark coil is used in starting, while the magneto is used for regular running. The spark coils and switches are located on the dashboard. A lever on the steering wheel, as will be described, is connected with the commutator or timer T7. which distributes the current to the six cylinders in such a way as to enable the operator to advance or retard the spark at will.
The Carburetor and Fuel Supply
An important and rather delicate piece of apparatus essential to the operation of the gasoline engine, is the carburetor, shown at Z in
Fig. 7. Clutch and Transmission Gear Members Dismantled to show Construction
Fig. 5. This receives a supply of gasoline through a feed pipe from the tank G (see Fig. 2), a supply of air through T heated by the exhaust gas for vaporizing the gasoline, and a supply of fresh air to furnish the oxygen for the charge. The gasoline is received in a float chamber, where the level of the liquid is maintained by a suitable float and valve. An automatic valve provides for a constant propor- tion of oxygen and fuel at widely-varying speeds. The carburetor is provided with a throttle which controls the needle valve connection in the feed pipe, together with the butterfly valve in the suction to the cylinders, thus providing the driver with means for varying the amount of charge furnished the machine; this controls the speed without shifting the gears in the transmission case. The automatic air valve is controlled from the seat by a handle Y on the dash-board, which permits the obtaining of a proper mixture for the starting. A button at the front of the radiator, where the machire is cranked for
10
No. 60— AUTOMOBILE CONSTRUCTION
starting, also provides means for flooding the carburetor with fuel for a send-off. The throttle is controlled from a lever on the steering wheel, concentric with the spark control lever, or from an "accelerator pedal" on the foot-board.
The gasoline supply tank O is located under the front seat. It con- tains a partition near the bottom which saves about three gallons out of its twenty gallons' capacity, for use in emergency. By the manipu- lation of cut-off valves passing through the left side frame of the chassis, it is possible to use this reserve supply after the tank has .been otherwise exhausted. This provision is a great comfort to the motorist at critical times.
The Clutch and the Transmission Gearing
In casing E is mounted the clutch Z (Fig. 7) connecting the engine with the transmission to the driving wheels. This is of the multiple
Slack inery,N.Y
Fig. 8. Sketch showing Arrangement of Gears in Transmission Case
disk type, with alternate disks keyed to the driving and driven mem- bers. The driving disks have a wired asbestos facing which makes a superior friction surface, and gives a high resistance to heat as well. This construction obviates, and in fact makes impossible, the use of oil in the clutch. The friction surfaces are held in engage- ment by a spring, and are released by a pedal Blt which projects through the foot board at the driver's side of the machine. The spring is so proportioned as to give a smooth, easy engagement, en- tirely out of the control of the driver, who thus finds it impossible to start the machine with a sudden shock. The second foot lever, Clt is connected with the rear wheel brakes, as will be described. The driven member of the clutch is connected with the driving shaft in the transmission case or speed box F. Contained within it is a mechan- ism which, by the aid of the sliding gears, clutches, etc., permits of the obtaining of three forward and one reverse speed.
The operation of this gearing will be understood from the sketch shown in Fig. 8. Gear A, receives its movement from the clutch. It meshes with gear Dt keyed to the secondary shaft E,, which is thus in motion whenever the engine is running and the clutch is engaged. This shaft carries also gears Gn #„ and Wlt the latter of which drives, in turn, the idler X^ Squared shaft Yj is directly connected by means
DESIGN OF A HIGH-GRADE MOTOR CAR
11
of propeller shaft J (Fig. 3) and the universal joints with the rear axle. On Ya is mounted the double sliding gear Zt. Clutch teeth are provided in the faces of the gears A, and Jlt
In the position shown in Fig. 8, the transmission is in the neutral position, so that the motion from the clutch is not transmitted to the axle. The right-hand end of shaft Yj lies loosely in the revolving gear AI. When the sliding gear is thrown to the extreme right, the clutch faces of Aj and Jt are engaged, so that shaft Y, is driven directly, and at the highest speed, from the clutch. By shifting it a step to
Fig. 9. The Speed Gear Control and Emergency Brake Levers
the left, /! is thrown into mesh with Glf thus giving a lower rate of speed through the back gear shaft Ev. A still further movement to the left, past the neutral point shown in the engraving, brings Zj into engagement with Hlt giving the lowest forward speed. A final movement to the left engages Z: with idler Xlt thus reversing the drive.
The shifting of gears Z1 and J1 is effected by a forked lever con- nected with lever A2 (Fig. 9) at the side of the machine, which thus controls the speed changes. This lever is provided with a latch con- nected with a pin in the slot of the quadrant B2, operating in a man- ner easily understood from the engraving. It will be seen that it is possible to move between the reverse and the lowest speed, or between the second and the high speed, without touching the latch, and it is possible to make all the movements rapidly and precisely by the sense of touch without looking at the quadrant at all.
12
No. 60— AUTOMOBILE CONSTRUCTION The Differential Drive
Propeller shaft J leads from the transmission case F to differential case A' on the rear axle. The bevel gear MI (Fig. 11) is connected with the two rear wheels by a differential mechanism, whose function it is to give an equal tractive force to each of the two wheels, but at the same time to permit either of them to run ahead or lag behind the other as may be required in rounding curves, riding over obstruc- tions, ejc. The principle of this mechanical movement will be under- stood by referring to Fig. 10.
Referring first to the sketch at the left, NI is the pinion on the pro- peller shaft and MI is the driven bevel gear, concentric with the axle.
Fig. 1O. Sketch showing: Principle of the Bevel and Spur Gear Types of Differential Gearing:
This gear and shell O2 to which it is bolted, revolve freely on the hubs of E2 and F2. Within the shell are mounted radial pivots on which revolve, loosely, bevel pinions D>. These engage with bevel gears Ey and Fs, connected respectively with the right- and left-hand axle shafts Tj. It will be seen that under ordinary conditions the rotating of gear Mt carries gears E~ and F, along with it, by the pull exerted on them by the bevel pinions D.., which are stationary; thus the two rear wheels are driven at the same rate of speed. Suppose now that the right-hand wheel be held from turning, so that gear JE7, is station- ary, then the rotation of bevel gear M^ will roll pinion D, about on #2 with a compound action, which will give F, twice the rate of speed it had before. In the same way, F, can be held from revolving, in which case E2 will have twice its normal speed, or either of them may be slowed down, in which case the other is speeded up corre- spondingly. The driving force on both wheels, however, is always the same.
DESIGN OF A HIGH-GRADE MOTOR CAR
13
An alternative form of this device is shown at the right of Fig. 10, in which each of the bevel gears D, is replaced by a pair of spur pin- ions D2 and Z>'2) meshing with each other and with spur gears E2 and P., as shown. A little study will show that the action of this device is identical with that shown in the sketch at the left of the figure, the only change being the employment of spur gearing in place of bevel gearing. The differential used on the Stevens-Duryea ma- chine is of the second or spur gear type.
The Pull Floating- Type Rear Axle
The differential gearing is contained in the casing 0,, which forma the central member of the axle. Tubular extensions to both sides
Fig. 11. The Full Floating Type Rear Axle, Differential Gearing, etc.
carry the spring supports P. on which the weight of the car rests. The brake flanges Qt and the wheel bearings at Klf all of which are solid with each other, are non-rotating. The rear axle, however, is permitted to rock in spring supports Pt. The torque rod or tube £„ which is fast in case Olf extends toward the center of the chassis, where it is hung in a spring suspension as seen in Fig. 3 permitting a limited vibration up or down, with a constant force urging it toward a central position. This construction furnishes the resistance against the climbing of pinion Nt on bevel gear Mt. In case of sudden start- ing or stopping, a limited amount of climbing either way is permit- ted, the torque rod being raised or lowered against the spring pres- sure to correspond. This greatly decreases the danger of gear breakage.
14 Xo. 60— AUTOMOBILE CONSTRUCTION
The construction just described belongs to what is known as the full floating type axle. The wheels are mounted on ball bearings on stationary journals J?,. Shafts 7\ are provided with squared driving ends engaging sockets in the differential gearing in casing Ot at one end, and similar sockets cut in driving dogs Ul at the other end. These latter members hav* driving slots engaging dove-tails in the hubs of the wheels, to which the power is thus transmitted. The squared ends of shafts 7\ are rounded to permit a slight rocking movement in their sockets in the differential gearing and driving dogs U^ This permits the springing of the rear axle under the load with- out, cramping the driving mechanism.
To allow for the springing of this axle under the load, the two sections of tubing on either side, between members Ox and Qt ar.e •held in bored seats which point downward at an angle of % degree from the horizontal on each side. Thus the rear axle wheels point in toward each other at the bottom at an angle of */£ degree from the vertical, giving a much better appearance than would be the case if they should by some mischance point the other way. It would take a load in excess of any which would ever be applied to spring the axle and bring the wheels into the vertical plane. It is stated that when the wheels are exactly vertical, they have the appearance of being sprung out at the bottom, into the position occasionally seen in a vehicle of the "one-horse-shay" type.
The Brakes
The brake mechanism of the automobile is of the utmost import- ance, as is realized by anyone who has had anything to do with these machines whether as driver, passenger or pedestrian. It is usual to provide two complete sets of braking machanism, one for regular use and the other for emergency. That for regular use is controlled by the foot lever Cl (see Fig. 4), which is connected with a reach rod leading to double cranks on a transverse rock-shaft at Vt (Fig. 3). One section of this rock-shaft is connected with the brake at the right side of the machine, and the other at the left. An equalizing lever between the two insures an even pressure on each of these two brakes, even though one be much more worn than the other. The brake is of the band type, applied to the outside of a brake rim fast to the hub of the wheel. The emergency brake is operated by lever C2 (Fig. 2). This, by means of a second rock-shaft concentric with Vlt controls internal expanding ring brakes in the hubs of the wheels.
The Control of the Machine
The steering gear will be best understood from Figs. 2, 3 and 12. The wheel Ft is mounted on a tubular shaft which carries at its lower end a worm engaging the segment of a worm-wheel G2 in casing Elt To the hub of this segment is connected a bell crank //., which, through -the operation of the steering rod L^ (see Fig. 2) and suitable connecting cranks and links, turns the front wheels to the right or left as may be required. Spring cushions are provided at the ends of steering rod Li so that sudden shocks and twists of the wheels are
DESIGN OF A HIGH-GRADE MOTOR CAR
15
not transmitted to the worm-gearing and the steering wheel, even when traveling at a high rate of speed. As most mechanics doubt- less know, the center line of the pivots about which the wheels are swiveled meets the road at about the point where the tire touches it. This makes it possible to turn the wheels easily when standing still, and decreases the danger of accident while running, as well.
As previously stated, the throttle control and the timing of the spark are effected frcm levers placed at the hub of the steering wheel.
Fig. 12. The Steering Post, with its Throttle and Sparking Connections
Lever K2 controls the throttle. This is mounted on a tube passing through the steering wheel tube and connected at its lower end by bevel gear segments with a bell crank L2, which is, in turn, con- nected by suitable rods and levers with the carburetor. Inside of the throttle lever tube is still another fixed tube on which is mounted the segment Af2, which is thus held stationary. This is provided with notches for locating lever K», and lever /2 as well, which latter con- trols the timing of the spark. This is mounted on a rod which passes through the center of the system of tubes and is connected by bevel segments with lever N* leading to the commutator or tinier V.
16 No. 60— AUTOMOBILE CONSTRUCTION
It may be well to recapitulate as to the functions of the levers, etc., used in the control of the machine. At the front of the radiator is the crank by which the motor is turned, for starting. By the side of it is a button connected with the carburetor, for flooding the latter at starting to obtain a rich mixture on the first stroke. On the dash- board is mounted a lever 3', for setting the automatic air valve to supply the proper amount of oxygen for starting. Beside it is a switch for throwing the ignition spark from the battery to the mag- neto when the machine is changed from the starting to the running condition, and vice versa. On the dashboard are also mounted the spark coils. Through the foot board project the two pedals Bl andCt controlling the clutch and the operating brake respectively, as de- scribed. Hand lever C, and A, control the emergency brake and the speed changes respectively.
Two small pedals are also provided on the foot board. One of these is connected with the throttle in such a way that this may be controlled by the foot instead of by the hand if required. It is called the accelerator. By its use, when the hand throttle lever has been set to a certain point, the valve may be opened clear out to the maxi- mum, as desired, by the foot, thus giving immediate control under varying conditions of traffic. The other pedal operates a valve which cuts out the muffler. This is occasionally done to make the exhaust audible, for finding out how the engines are working, and also for removing the back pressure, and thus giving every ounce of power possible on critical occasions.
These levers, pedals, etc., with the main and supplementary gaso line supply valves previously mentioned, give the driver complete control of a powerful, swift machine, if he has the knowledge, experi- ence and nerve to use them properly.
General Considerations in Automobile Design
A glance at the illustrations will serve to show that the chassis of the modern high-power automobile is a rather complicated, highly specialized, and carefully designed piece of mechanism. It is within the memory of the child in kindergarten when this was not the case, and the writer has painful memories of his duties as consulting phy- sician to one of the best of the machines in existence six years ago At that time, the mechanism of the automobile did not have the homo- geneous, appropriate structure that the successful machines of the present day jmssess. It had a gasoline engine, an epicyclic speed change mechanism, a jack-in-the-box differential gear, and chains leading to the rear wheels of a "horseless carriage." Over the mechan- ism thus described wandered a maze of levers, braces, pipes, wires, etc., supported at intervals at any part of the mechanism which hap- pened to be in convenient reach. That, however, was before the auto- mobile "found itself." The present development has been the result of the experience of many men with break-downs and failures, as well as of an enormous amount of theoretical work in the matter of test- ing of materials and analysis of conditions. These theoretical and practical results have been combined on the drawing board, and the
DESIGN OF A HIGH-GRADE MOTOR CAR 17
resulting machine has the appearance of having been designed rather than simply built.
The guiding principles in the design of the automobile relate to strength, power, lightness, durability, accessibility, and economy in operation. The matter of economy in construction and materials is about the last thing to be thought of, instead of the first, as with many other classes of machinery. The severe and often reckless usage received by one of these machines demands special treatment in the design and construction which should not ordinarily be necessary.
As an illustration of what has been said in this respect, attention may be called to the method of connecting the driving members of this machine, from the engine through to the wheels. In no place throughout the length of the chassis are keys used for this work. Reli- ance is everywhere placed on square joints or dovetailed flanges. The crank-shaft is connected with the .driving member of the clutch by a square taper socket. The driving member of the clutch is connected by a square socket with the driving shaft of the transmission gear- ing. The sliding gears of this mechanism are mounted on square shafts, and the same squared drive is used for the universal joints, propeller shafts, pinion shafts, etc., through the intermediate pinions in the differential gearing at Ml in Fig. 11, and through driving shafts Tv to the driving dogs on the wheel hubs. These latter, as well as the side plates of the differential gearing, drive or are driven by the engagement of dovetailed teeth. The possibility of the shearing of keys, always present in machine parts subject to shock, is thus avoided. The makers believe themselves to be the only firm employ- ing a complete drive of this kind.
In the matter of accessibility, a study of Figs. 6 and 7 will be found interesting. By removing the lower crank chamber casing and turn- ing the crank-shaft to the proper position, the piston and piston rod may be removed without further trouble, and without removing cylin- ders or cylinder heads. The same is true of the cam- and lay-shafts. The covers provided for the clutch and transmission casings give evi- dence of care in providing easy means for inspection and removal of all parts likely to need attention. With a well-designed machine the man on his back under the motor car is a mere figment of the imagina- tion.
CHAPTER II
AUTOMOBILE MANUFACTURING METHODS*
The subserviency of manufacturing considerations to considerations of strength, durability, accessibility, etc., mentioned in the preceding chapter, results in the design of parts which require special and inter- esting provisions for their economical production. Only a few of the operations particularly noticed in the Stevens-Duryea factory will be described here. They will serve, however, to give an idea of the gen- eral practice in such work, and will illustrate the ingenuity required for the solution of some of the problems.
Operations in the Machining- of Cylinders
In Fig. 13 is shown a Beaman & Smith combined horizontal and vertical milling machine engaged in surfacing the base, exhaust and
Fig. 13. Gang Milling Operation. Surfacing Cylinder Sides and Ends
inlet flanges, and the spark plug bosses of a series of cylinder castings. The work is mounted in gangs according to the most approved methods. The picture is chiefly interesting in that it shows that the builders take advantage of wholesale manufacturing methods even in the building of a $4,000 machine. Of course, an extensive use of jigs and fixtures, besides reducing the cost of manufacture, results in a greater uniformity in the product, and thus gives the advantage of an easy renewal of worn or damaged parts.
Fig. 14 shows a Beaman & Smith boring machine with fixtures mount- ed on the rotating table for holding four double cylinder castings. This table can be rotated and adjusted across the bed of the machine.
* MACHINERY, October, 1909.
MANUFACTURING METHODS
19
On each side of the table, double boring heads may be fed in along the bed, one carrying roughing and the other finishing cutters, the feeds and speeds of the two heads being independent. A set of two castings being in place on the roughing end, the head is fed into them and one hole in each casting is roughed out. The work-table is
Fig. 14. Four-cylinder Boring Machine with Revolving Table
Fig. 15. Grinding the Cylinders. Note Connections for Exhausting the Dust and the Use of the Water Jacket for Cooling
then shifted, by means of the hand-wheel, against suitable stops, and the other bore of each cylinder is roughed. The table is then indexed to bring these castings to the finishing side, where the same operation is repeated, the boring being here carried to size for grinding. This rotating of the table, in turn, brings a new set of the cylinders up to be rough-bored. The process is continuous, the work being removed
20
AV. 60— AUTOMOBILE CONSTRUCTION
from the finishing side and new cylinders clamped in, while the rough boring is being completed.
For setting out the cutters in the boring bars, the construction shown in Fig. 16, at the left, is used. It will be seen that a taper- headed screw is used for forcing the blades out simultaneously. The cutters B bottom, on this taper-headed screw C; fillister head screws D serve to keep the blades forced down to their bearing on C, and so draw them firmly against the side of the slot. By this means two or more blades may be set out simultaneously for regrinding to exact size. A similar arrangement (see view at the right of Fig. 16) is used for cutters in the middle of long boring bars, except that the taper point of a screw tapped into the bar from the side, is used in place of the corresponding taper-headed screw in the first case.
ADJUSTMENT FOR END CUTTERS
ADJUSTMENT FOR
CUTTERS IN CENTER
OF BAR
Machinery, .\.X
Fig. 16. Adjustment used for Boring-bar Blades
The bore of these cylinders is finished in Heald internal grinding machines especially built for this work. These are of the type in which the work remains stationary while the axis of the spindle is revolved about the center line of the bore and parallel with it, on such a diam- eter as to bring the outer periphery of the wheel in contact with the inner surface of the bore. The grinding spindle is fed out so as to rotate in a larger circle as the diameter of the bore is increased. An interesting feature shown in Fig. 15 is the provision of a flexible suc- tion tube for drawing out the dust of the grinding through the inlet and exhaust ports, and also the provision made for water cooling. The water is not applied directly to the wheel, as in an ordinary external grinder, but is forced instead through the regular water jacket of the cylinder casting. This reproduces, in a measure, the con- ditions met with in actual use, and so tends toward accurate work.
Machines and Fixtures for Grinding- and Lapping- There are other operations of interest in the grinding department besides that of finishing the bore of the cylinders. Extensive use is made of the Pratt & Whitney face grinding machine for finishing flat -nrf;t<M's: in fact, it lias largely displaced the vertical milling machine for this work, on parts in which the surface to be finished is clear of projections or obstructions to the sweep of the wheel. The faces of
MANUFACTURING METHODS
21
the various casings, covers, inlet and exhaust pipes, etc., are finished on this machine. In the past most of these parts have been made from castings on which 3-16-inch of stock had been left, in accordance with the usual practice of milling. The castings come true enough to shape, however, to permit of this finish being reduced to 1-16 of an inch, or
Fig. 17. The Acme of Simplicity in Fixture Making. Face Grinding the Steering Gear Casing
Fig. 18. Grinding the Bore of the Cams Concentric with the Cylindrical Surface
thereabout, when finished by grinding, thus materially reducing the time required. Even when removing 3-16-inch of stock the grind- ing machine has proved its superiority to the milling machine in the matters of cost, finish and accuracy. The foreman of the grinding department discovered that a little experimenting and investigating along the line of the grading of wheels made a tremendous difference
22 No. 60— AUTOMOBILE CONSTRUCTIOX
in their durability and effectiveness in removing metal. For aluminum work a vitrified carborundum wheel of about No. 24 grain and grade H hardness is used, a soda compound being employed for cooling.
The cover side of the steering gear casing is one of the parts sur- faced on the face grinder. An exceedingly simple fixture is used for holding it. This fixture, as may be seen in Fig. 17, is nothing more or less than a mass of lead melted and poured around a sample casting as a form. The work is set into the bed, thus prepared to receive it, and is supported on the table by its own weight, no fastening being uecessary. The castings come uniform enough so that they fit well in this device, except at certain points around the gates and sprues, where it is found necessary to relieve the form slightly to allow for these variations. It may be mentioned that the other or main member of the steering gear casing has a boss projecting above the finished
GUIDE SURFACE
TABLE OF PROFILER
Fig. 19. The Simplest and Stiffest Arrangement for Cam Cutting
surface of the joint, making it necessary to mill that surface. The joint is thus formed of one ground and one milled surface.
In Fig. 18 is shown the operation of grinding the holes in. the cams. It is quite important that the cylindrical portion of the cam shall be exactly concentric with the cam-shaft to prevent shock or jar during the period "when the valves are supposed to be closed. To make sure that this surface is concentric, the cam is located by it in the grinding fixture as shown. After the fixture has been mounted on the faceplate of the machine, the gripping surfaces of the two jaws at the right are ground out by the internal grinding attachment, to the radius of the cydindrical dwell of the cam. The cam is clamped against the surface thus prepared, by the lever, which forces a wedge across and down upon the cam, holding it firmly into the corner in both directions.
It will be seen that this car does not employ the integral cam-shaft. By giving careful attention to the locating of the cams on the shaft and by being careful to obtain a strong drive fit between them, the difficulties of loosening and dislocation, which the integral construc- tion is expected to cure, have been avoided. It is thus permitted to cut the cams in a way which gives the best chance for producing accur- ate shapes and smooth finish. The obvious scheme shown in the
MANUFACTURING METHODS
23
sketch, Fig. 19, is followed, the operation being performed on a profiling machine. The connection between the forming cam and the work is so close that the difficulties of springing and chattering, met with in the construction of the more elaborate machines required for integral cam-shafts, are avoided.
Another faceplate fixture for internal grinding is shown in Fig. 20, where it is employed for grinding the hole in the hardened nickel steel sockets used for the universal joints (see Fig. 7, Chapter I). The socket is held in the same way as when in use, by a nut screwed onto its threaded shank. It is also located in the same way, a pin in the fixture engaging a slot in the flange as shown. A limit of 0.0005
Fig. 2O. Grinding the Holes in the Universal Joint Pivots
inch only is permitted in this operation, : and an allowance of about 0.003 inch for the depth of the hole is the maximum, just enough being permitted for proper lubrication by the grease supply provided. This fixture is kept in place on the machine practically throughout the season. If at any time it is necessary to remove it, however, it can again be trued up by clamping a model socket in place, inserting a plug in the ground hole, and truing up the plug. These studs are held in, the same way in the screw machine for roughing out the hole preparatory to grinding. The form of internal grinding spindle used should be noted. One of them is shown detached in Fig. 18, lying on the table of the machine. These spindles and their bearings are self- contained, interchangeable and adapted to work in holes of various sizes. The clutch drive provided rotates the spindle without side pres- sure on the bearings.
Machining- the Members of the Squared Drive
As previously mentioned, the use of keys is eliminated in the drive of the Stevens-Duryea machine, their place being taken by square sockets throughout. A tapered square drive is used to connect the
24 Xo. 60— AUTOMOBILE CONSTRUCTION
crank-shaft with the driving member of the clutch. The method of machining this is shown in Fig. 21. It has been found advisable to keep the milling machine set up for this work, continuously, owing to the difficulty of making a good taper square fit. When the machine has once been set, it is kept so throughout the season. An ordinary dividing head is used, as shown, tipped up to the angle of the taper. To the faceplate of this dividing head is clamped the fly-wheel flange of the crank-shaft. The outer end of the crank-shaft is supported in a suitable steady-rest as shown. For shorter lengths of crank, filling pieces are employed, having flanges bolted to the faceplate at one end, and to the work at the other. The use of filling pieces permits machin- ing of the full line of crank-shafts without disturbing the adjustments.
Fig. 21. A Vertical Milling Machine set up for Milling the Tapered Square Drive on the Crank- shaft
The automatic cross-feed is employed in feeding the work past the end mill in the vertical milling attachment. Tne table has to be so far overhung that an out-board support is provided as shown, which permits this cross-feed. This consists of a sliding guide, supported by two standards, reaching to the floor and provided with jack screw adjustments for careful leveling.
The squared holes of the drive are finished on a La Pointe broaching machine in the usual manner. The further machine shown in Fig. 23 is engaged in finishing taper square holes in the clutch driving flange, this being the member into which the taper squared end of the crank-shaft shown in Fig. 21 fits. The hole is first reamed out to a taper a little larger than the distance across the flat of the finished hole. The work is then mounted on a broaching machine on the fix- ture shown in place. As may be seen, the broach cuts one corner of the square hole, and one-half way up each of the two adjacent sides, into the relief formed by the taper hole. A dog is fastened to the hub of the work, and the latter is mounted on a taper plug fitting the hole, with the tail of the dog located by a pin in the faceplate of the fixture,
MANUFACTURING METHODS
25
the latter being mounted on the faceplate of the machine at an angle as shown, to agree with the angle of the corner of the tapered sides.
One pass of the broach finishes one corner of the tapered hole. The broach is then returned to the starting position, the work is drawn off the taper plug, the dog indexed to the second pin on the faceplate, the work is put in position and the second corner broached. This operation is repeated until the four corners have been machined, and the square hole finished, the work being centered on the taper plug of the fixture throughout the whole operation. A taper square gage is shown lying on top of the broach in the engraving. This is used for testing the fit of the holes and the accuracy of the work, and a most accurate fit is made on this by no means easy operation. In the machine in the foreground, another operation is being done — that of
FACE PLATE OF BROACHING MACHINE
SIZING TOOL, WITH SUCCESSIVELY LARGER BEADS
Fig. 22. Method of Sizing Phosphor-bronze in the Broaching Machine by Compression
broaching the driving slots in the driving clutch members for the mul- tiple disks.
Sizing- Round Holes in the Broaching- Machine
Another unusual operation for which the broaching machine is here used, is that of sizing holes in hard phosphor-bronze bushings. This material, as any mechanic who has had any experience with it knows, is as hard on a finishing reamer as anything well can be. It is tough, elastic and slippery, and the less there is to ream the more difficult becomes the operation. Instead of reaming such holes, the tools shown in Fig. 22 are used in this shop. It will at once be seen that the opera- tion is that of compressing the metal in the sides of the hole, until it has been enlarged to the finished size. The tool is drawn through the work. Each of the rounded rings or beads is a little larger than its predecessor, thus gradually compressing the metal the desired amount. The finished hole springs to a size smaller by some few thousandths than the diameter of the largest ring on the tool, so that the size of the latter has to be determined by experiment. This allow- ance varies slightly also, as may be imagined, with the thickness of the wall of metal being pressed. In such a part as that shown in Fig. 22, for instance, after drawing through the sizing tool in the broach- ing machine, it will be found that the hole will be somewhat larger in the large diameter of the work than in the hubs. It has been found that this difference in size can be practically avoided by passing the
26
No. 60— AUTOMOBILE CONSTRUCTION
sizing tool through the work three or four times. Few pieces of this kind are found, however. The operation is a rapid one as compared with reaming.
An Adaptable Lapping Machine
The machine shown in Fig. 24 was built mainly in the factory, use being made, however, of the adjustable columns of a Taylor & Fenn
Fig. 23. A Set of Interesting Broaching Operations
Fig. 24. Machine for Circular and Square Lapping Operations
sensitive drill press. This special machine is intended for lapping out the square holes of the drive, but is provided also with a rotary movement in addition to the vertical movement thus necessary, so as to provide for cylindrical lapping as well. The driving pulley at the right gives the reciprocating motion, while the pulley at the left rotates the spindles through the medium of the regular geared speed
MANUFACTURING METHODS 27
drive. The sprocket wheels shown, driven from the right, are loose on the driving shaft, and carry eccentrics whose rods are extended to form racks engaging, through a suitable clutch connection, the pinion shafts by which the spindle quills are fed up and down. It is thus possible to give a rotating and reciprocating movement to the spindles, either together or separately.
Separating- Piston Ring's
Another milling operation is shown in Fig. 25. It is a common practice to make piston rings on an automatic machine specially rigged up for the purpose, separating the rings from the finished casting by means of a series of parting or cutting off tools, each of
Fig. 25. Cutting out Piston Rings in the Vertical Milling Machine
which is set a little in advance of the other so that the rings will cut off in regular succession. The parting tool, however, especially when used in severing cast iron work like this, having an eccentric bore, leaves a considerable burr. In the method of severing the rings shown here, the eccentric cylinder is first finished complete on the turret machine. Then it is mounted on an internal expansion chuck on the faceplate of the cylindrical attachment of the Becker vertical milling machine, as shown. This chuck is provided with clearance grooves for the gang of saws shown in the engraving. These are sunk into the cylinder, and then the work is rapidly revolved, cutting out the eight rings at once. The saws are permanently mounted on their arbor, with separating collars ground to the proper thickness.
Examples of Fixtures Used for Drill-press Operations
The drilling department seems unusually small, when compared with the size of the whole plant, and gives the appearance of being worked at high pressure. The large output required is evidently maintained by the universal use of highly developed jigs for all
28 No. 60— AUTOMOBILE CONSTRUCTION
manufacturing operations. Multiple spindle drill presses are used to almost the entire exclusion of the single spindle type.
Fig. 26 Is interesting as showing the development of the jig for a comparatively simple operation — that of drilling the cotter pin hole in a headed cylindrical stud. In the first apparatus employed (not shown) the stud was pushed into a hole up to its head, and held there by a lever, one piece being done at a time. This rigging had two faults. One piece at a time is held, and trouble with chips and burrs was experienced, as might be imagined. An improvement on this device is shown in the two jigs at the right, where a base with a set of V's is provided in which several of the pins may be placed, their heads being pressed up against the end of the V-block by
Fig. 26. Interesting Drill Jig's for a Simple Operation
springs. The cover being clamped down on the work, the parts are thus held for the drilling operation. This, however, was not quite easy enough to clean to suit the ideas of the tool designer, so the fixture shown at the left was used for the next tool of tnis kind that had to be made. Here hinged sides are used instead of springs as in the previous case. These sides fold up and press the heads of the work against the edges of the V-block. When they are turned down and the cover of the V-block is raised, the top surface of the V-block is all clear, so that the presence of chips shows inexcusable careless- ness on the part of the operator. When the sides are folded up against the work and the cover is brought down, the latter, by means of wedge" surfaces, presses the sides in, holding the heads of the work firmly in place and clamping them down on the V-block at the same time.
The jig shown at work in Fig. 27 is used for drilling and reaming the connecting-rod holes. It is of the "four-legged table" variety, with suitable clamps and hook bolts for taking the strain of the cut with- out permitting noticeable deflection and consequent inaccuracy in the
MANUFACTURING METHODS
29
work. A feature of the construction which is, perhaps, old enough, but probably new to many, is the provision made for both drilling and reaming with a fixed bushing, thus avoiding the use of slip bushings of different diameters. For drilling, the jig is used as shown in the engraving, with the work clamped beneath the plate and the jig bush-
. 27. Gang Drill used in Drilling and Reaming Connecting-rod Ends
Fig. 28. An Unusual Array of Automatic Chuckinar Machines ; Thirty-one are used in this Department
ings above, guiding the drills. Fpr reaming, the jig is reversed and a reamer is used having a pilot, which passes through the work into the jig bushing (now on the under side of the plate) by which it is guided.
Fig. 28 shows what is by long odds the largest aggregation of auto- matic chucking machines the writer has ever seen. There are thirty-
30
60— AUTOMOBILE CONSTRUCTION
one of the Potter & Johnston type. Practically every turned part not made in the screw machine from the bar is produced on these ma- chines. That old standby, the engine lathe, appears to be about the rarest machine tool in the shop.
Fig. 29 shows a section of the engine assembling room. It will be noted that machine tools are few and far between, the only ones in
Pig. 29
Engine Assembling Department
sight being a drill press, speed lathe, and two or three grinding stands for sharpening tools. This shows that the manufacturing operations have been performed with great exactness. The question of assembly is simply one of bolting and screwing the separate parts together. The engines here shown are of the four- and six-cylinder type. The overhead trolley lines should be noted.
CHAPTER III
MANUFACTURING AUTOMOBILE EQUALIZING GEARS*
The present chapter deals with operations which do not present any especially unusual or spectacular features, yet they have a valne derived from the fact that they are closely related to the operations which produce the bulk of the product of the machine shops of the country; for that reason they should attract the attention of mechanics interested in accurate and economical work. The operations for mak- ing a complete, compact machine unit — a differential or equalizing gear for automobile use, is described from beginning to end. The com- pleteness of the job gives it a suggestive value that would not be
Fig. 3O. The Equalizing Gear Complete, with Bevel Gear and Pinion
offered by a series of miscellaneous operations, however interesting.' The value of this description, however, does not depend on its com- pleteness alone, as many of the specific shop operations give evidence of a high degree of manufacturing ability.
Description of the Equalizing1 Gear
Figs. 30, 31 and 32 show assembled, dismantled and detail views, respectively, of an equalizing or differential gear, designed by Mr. A. A. Fuller, of the Providence Engineering Works, Providence. R. I. The determining feature of this design is the necessity for getting a maxi- mum of strength and effectiveness in a minimum of space — coupled,
* MACHINERY, December, 1909.
32
No. 60— AUTOMOBILE CONSTRUCTION
of course, with reasonable cost of manufacture. This problem was attacked by scientific analysis. It was possible, without great diffi- culty, to obtain reasonable strength in the casing which contains the equalizing gearing. The crucial point was in the design of the equal- izing gears themselves. In determining the proportions of the gears, curves were drawn showing the strength of the teeth for lay-outs of varying pitch and number of teeth, arranged to be contained within a casing of a given diameter. The strength and bearing area of the pivots, and the strength of the pinions as limited by the thickness of the shell between the bottom of the tooth and the bore, had also to be reckoned with. The tooth shapes were not confined to standard forms, but various pressure angles and heights of addendum were
Fig. 31. A Small Size of Equalizing Gear Dismantled to show Construction
investigated. By comparing the curves for various possible designs, a certain pitch, number of teeth and shape of tooth for the various gears were found for each diameter of casing, so proportioned that if any of the dimensions were changed, the mechanism became weaker • instead of stronger. These proportions, worked into a design satis- factory in other particulars, have been adopted as standard, and the makers feel confident that it is impossible to enclose in the same space gears of greater strength than they are offering in the design illus- trated herewith. As this confidence is based on mathematical calcu- lations and has been further tested by many months of experiein •• .-. it. seems reasonable that they should hold to it.
Referring particularly to Fig. 32, the mechanism is contained within case B and covers A and A'. It revolves in the rear axle gear casing on ball bearings, mounted at the ends of casings A and A', and the driving bevel gear is carried on the periphery of case B, to which it is clamped by hexagon-head screws H. The pivots E are riveted into
MAKING EQUALIZING GEARS
33
the flanges of covers A and A', three in one side and three in the other. These pivots carry pinions F and F' meshing with gears C and C"; the latter run in bronze bushings D and D' forced into the two covers, and are provided with broached square holes by which the floating wheel shafts are driven. As will be seen in Fig. 31 in connection with Fig. 32, gear C meshes with pinion F\ which also meshes with pinion F, the latter in turn engaging gear C". Thus, when gear C is turned, gear C' is revolved in the opposite direction, and vice versa, thus form- ing a spur gear differential mechanism.
Attention may be called to some of the features which make for strengtlj. in this design. It will be seen, for instance, that the gears have teeth of special shape and of very coarse pitch and few numbers of teeth. The pinions have eight teeth and the gears sixteen each. In
Fig. 32. Details of Construction of the 7-inch Equalizing- Gear
designing the mechanism .by analysis, as described, it was found that this construction was necessary for strength. Older designs of this kind, more commonly met with, in which the pinions are smaller in proportion to the gears, have repeatedly proved their weakness by breakage.
Mention should also be made of the solid way in which the parts composing the casing are fastened together. The casing B is provided with tongues locking into the grooves cut in covers A. so that the strain of transmission is taken on these interlocking members and is not taken by the bolts, dowel pins or similar parts. So far as this tor- sional strain is concerned, the casing is as strong as if it were made of solid metal — an impossible construction, of course. Through bolts and nuts G and G' clamp the whole casing firmly together.
The proper meshing of the bevel gears can be controlled by shifting the whole casing axially in its bearings. Nuts are mounted, for this purpose* one on the threaded diameter of A and the other at the same point on A'. By loosening one and tightening the other the teeth of the gears can be brought more closely into contact, or vice versa.
The provisions for oiling should be noted. The casing on the rear axle is provided with a bath of oil in which the bevel gears run. Three
34 No. 60— AUTOMOBILE CONSTRUCTION
holes cut in the exterior of B (not shown in Fig. 31, but visible in the detail views of the operations in Fig. 33, and at the right of Fig. 34, where these holes are being drilled) admit oil from this bath into the interior spur gears. Pivots E and pinions F are grooved, as are also gears C and C' permitting a flow of oil through the whole structure, kept in constant motion through the revolving of the parts.
In describing the manufacture of this device we will take up each part in turn. The manufacture of the bevel gears will not be described
Fig. 33. Milling the Drive Tongues In the Gear Case— Second Operation
in detail, as their design is determined by the maker of the car in which the device is to be installed. The first part to be considered will be the gear case, shown at B in Fig. 32.
Operations in the Manufacture of the Gear Case
The case is made from a malleable iron casting on which tin1 first operation, naturally, is that of snagging to remove fins, gates, etc. The second operation is performed in the Jones & Lamson flat turret lathe, of which large use is made in this1 shop. The casting is placed in the
MAKING EQUALIZING GEARS 35
chuck of the machine with the flange outward. In this operation the hole is finished to size, the flange is turned, and the projecting end is faced. The regular equipment is used for this purpose, the only special tools being gages for the inside diameter of the hole and the outside diameter of the flange.
In the third operation, performed in the same machine, the part is grasped by the finished flange in special soft chuck jaws, which have been turned in place to fit the diameter they are to receive. This givea assurance that the work done in this operation will be true, within reasonable limits, with the cuts previously taken. Regular flat turret lathe equipment is used for this operation as well, suitable gages of
Fig. 34. Drilling the Three Oil Supply Holes in the Case (see Fixture at the Right), and Drilling the Bolt and Pivot Holes in the Cover
simple construction being provided. The next operation, shown at the right of Fig. 34, is drilling the three holes which admit oil to the inter- ior of the case. This jig is of the simplest possible construction, con- sisting of a knee with a turned seat on which the work is placed, and an overhanging lug carrying a drill bushing. A clamp provides for holding the work, and a plug, entering a suitably located hole in the seat, pro- vides means for indexing the second and third holes drilled, from the one previously completed. The other operation shown in this engrav- ing will be described later on.
The tongues which interlock with the grooves in covers A and A' (see Fig. 32) have next to be milled. The fixture for doing this is shown in use in Fig. 33. It consists of a base provided with an index plate and a revolving table, by means of which the work may be indexed step by step to cut the various tongues. These are shaped by straddle mills which form the opposite sides of the tongues parallel, so that they fit into corresponding grooves milled into the covers by a straight-sided cutter. In the operation illustrated, tongues have been cut on one side
36
No. 60— AUTOMOBILE CONSTRUCTION
of the casing, which is located in its seat in the fixture by the inter- locking of these tongues with grooves provided to receive them as shown. This assures alignment of the cuts on each edge of the case. In the first operation the uncut edge of the work is simply set down onto
Fig. 35. The First Turret Lathe Operation in Finishing the Gear Case Covers
Fig. 36. Second Operation on the Flat Turret Lathe using Special Jaws
this seat. It is held down by three clamps, provided with noses which enter the three holes drilled to admit oil to the interior of the mechan- ism.
It is interesting to see the expertness with which the operator cuts cut these tongues. The automatic feed is set at the highest point
MAKING EQUALIZING GEARS
37
practicable when cutting the full depth. As this would be less than the maximum possible when the cutter is entering the work, he begins with a hand-feed at a considerably higher rate, throwing in the auto- matic feed when the cutter gets down to work. Although the machine is of modern construction, the workman feeds in all the belt can handle. The gear casing is now complete except for certain opera- tions performed on it in assembling, as described later.
Operations on the Gear Case Cover
The gear case covers are made from machine steel drop forgings. After the snagging, the first operation is the simple one of putting a 1^-inch hole through the center of the forgings. This is a drill press operation and is merely done to remove stock, it being, of
Fig. 37. Layout of Tools on the Flat Turret Lathe for the Operation shown in Fig-. 35
course, impracticable to form the hole in the forging. It is next clamped by the rim with the hub projecting, in the chuck of the flat turret lathe. This first turret lathe operation is shown in Figs. 35 and 37, the latter diagram indicating the arrangement of the tools.
The first cut is shown at A. An outside turning and boring tool, acting in conjunction, rough turns the hub and rough bores the hole. At the next station, B, three tools simultaneously face the end of the hub and the two surfaces of the flange. Two cuts are taken with these, one for roughing and one for finishing. A third cut is taken with the same tools fed axially against the work to form the two grooves in the face of the flange, as most plainly shown in Fig. 32. At the third station (7, another turning tool removes the stock on two diameters of the hub, two cuts being taken. At D a finishing cut is taken over the smaller diameter, while at E a form tool shapes that portion of the hub extending from the threaded diameter to the flange. This operation is completed in about 18 minutes.
33 No. 60— AUTOMOBILE CONSTRUCTION
In the second operation (see Figs. 36 and 38), the completed end of the piece is grasped in soft jaws turned to fit the surface they grasp, assuring true running of the surfaces made in the two operations. The tool at A bores out the large diameter of the hole, which is for clearance only. The reamer at B finishes the small diameter to size. The tool at C faces the flange, taking two cuts, one to rough out stock and the second to bring it to size. A flat-nosed tool at D finishes the flange. The tool at E roughs out the counterbore, while that at F finishes it. This latter tool is fed directly in, boring the diameter of the counterbore to size until the bottom is reached, when the slid- ing head is fed outward, so that the same tool faces the bottom of
Machinery, X.T. Fig. 38. Layout of Tools in the Operation shown in Pig. 36
the counterbore. The finishing is thus done by turning cuts instead of forming cuts, giving a higher degree of accuracy. Work of this kind shows the flat turret lathe to very good advantage. In the lay- out of tools shown in Figs. 37 and 38, there were probably no special tools of any kind required, with the exception of the form tool E, the rest being stock turning tools of the kind which form the regular equipment of the machine. It may have been necessary in some cases to give the tool a knock of the hammer on the blacksmith's anvil to bend it in one direction or the other, but nothing more would be needed. The cross sliding head and the multiple stops come into play in such operations as those at B and C in Fig. 37, and F in Fig. 38, giving each separate tool a wide range of usefulness, especially when it is so made that it can be used for both turning and facing jobs.
Of course there are all sorts of opinions about such matters, but in the question of hand i-cmitx automatic machines, this company
MAKING EQUALIZING GEARS
39
believes that the conditions favor the use of the hand turret lathe in its work. The simplicity of the tolling is an important factor on contract work. The management can never be sure of the long con- tinuance of any job, so that anything approaching costliness or elabor- ation is prohibited. Furthermore, it is reasonably certain that one hand machine will turn out more work than one automatic, particu- larly when, as in this shop, there is an inducement, such as the premium system, for the workman to get the very most out of his machine. He is constantly changing his feeds and speeds as the varying diameters, depth of the cut and condition of the tool require. He is thus able to take heavier cuts without injuring his cutting edges than would be possible without constant personal supervision.
Fig. 39. Milling the Driving Slots in a Pair of Gear Case Covers
Probably three or four changes are made in each operation to one that would be made on an automatic machine. As another advantage, this greater production of the machine means a much less capital- outlay per dollar of output.
It certainly does keep the operator busy to get the most out of one of these lathes. There is no possibility of his running more than one machine, on this particular work at least. Cuts are taken very rapidly and changes of feed and speed follow each other in constant succession. There is a line of demarkation at the point where the intensity of production on the part of the hand machine and the lower capital charge on machines, buildings, stock, etc., balance the higher output per man and the consequent lessened labor cost for the automatic machines. In accordance with their judgment, some shop managers will draw the line at one point and some at another. It is fortunate for the builders of both types that all men do not come to the same conclusion when reasoning from the same premises.
40
No. 60— AUTOMOBILE CONSTRUCTION
In Fig. 39 the milling machine is shown rigged up to cut the driving slots in a pair of the gear case covers. The two are mounted together face to face on a special iron arbor, having a driving tail cast integ- rally with it in place of the usual separate dog. A formed cutter is used which shapes the bottom of the slot to the true radius of the inside diameter of the casing B (see Figs. 32 and 33) assuring a tight fit. This operation and that shown in Fig. 33 have to be done to close limits with good indexing plates, only 0.001 inch variation being allowed on the thickness of the slot and the tongue. This means that in order to make a good fit the dividing must be very accurate. In the cases the writer has seen assembled, these parts drove together with a very little gentle urging from a lead hammer. Not much of
Fig. 4O. Jig for Drilling the Bolt and Pivot Holes in the Gear Case Covers. Another Jig for the Same Operation is shown at the Left of Fig. 34
anything else seemed to be required. In Fig. 40 is shown a jig for drilling the bolt and pivot holes in the gear covers. It is of simple construction, the cover being supported on four legs and located by a central spindle over which it is dropped and by which it is clamped, an open side collar and nut being used as shown. The bushing plate set over the work is located to* bring the holes in right relation with the slots, by a tongue entering the latter. In the next operation the covers are mounted on a special faceplate, as shown in Fig. 41. This faceplate is surfaced true in place and is provided with an expansion mandrel centered integrally with it. The gear case is slipped on over this mandrel and tightened in place by turning on a wedge screw. While thus held the countersink in the outer end of the hub, the seat for the ball bearing, and the threaded diameter are turned. The thread is also cut. This is done by the Rivett-Dock threading tool, shown in operation. These operations of countersinking, turning and threading, altogether, average about eight minutes time for each piece. When the turning was in progress, the writer timed the lathe
MAKING EQUALIZING GEARS
41
and found it was making 250 revolutions per minute, which gives about 150 surface feet per minute for the cutting speed.
A fixture and mill of obvious construction are used for cutting the keyway by which the inner race of the ball-bearing is made fast to the hub.
Equalizing- Pinions, Studs and Gears
Studs E, Fig. 32, are made on the Gridley automatic turret lathe with the regular tools and equipment, the job being, of course, one of the everyday variety for this machine. Oil grooves are milled, and then the burrs are removed by hand. The equalizing pinions are drilled, reamed and turned on the flat turret lathe. The ends are squared accurately to length in the engine lathe.
Fig. 41. Threading the Gear Case Covers with a Rivett-Dock Threading Tool
The equalizing gears are cut off to length from the bar stock (all gears and pinions are made of chrome-nickel steel) and are bored, reamed, faced and filleted at the large end in the Jones & Lamson machine. The hole is reamed accurately to size so as to furnish a guide for the broach in forming a square hole. This is done on the La Pointe machine at a single pass of the broach, which is a long one, having some 24 inches or thereabouts of cutting length. The outside surfaces of the gear are then rough turned on a square expan- sion chuck somewhat similar to that shown in Fig. 41 for the gear case cover, except, of course, that it is mounted on a square surface instead of a round one. In the next operation it is finish turned all over.
The spur gears and pinions are cut in a triple head indexing device which is one of the standard attachments on the Brown & Sharpe milling machine. Three cutters operate on three gangs of work simultaneously. By giving special shapes to the gears and by being very careful, both in centering the cutters and setting them to the
42 No. 60— AUTOMOBILE CONSTRUCTION
proper depth, first-class results have been obtained — better than are needed in fact, since normally these gears are stationary or nearly so, being in operation only when rounding corners, in the case of a deflated tire on one side, or the slipping of a wheel in the mud. After removing the burrs by file and reamer, the gears and pinions are hardened by the regular process recommended by the makers of the steel (the Carpenter Steel Co.), with such modifications as the black- smith of the shop lias found advisable.
The equalizing gear bushings D and D', Fig. 32, are cut from a bronze bar in the flat turret lathe, being turned and bored complete to size. A stack of them are placed on the Mitts & Merrill keyseater for cut- ting the internal oil grooves. The radial oil groove is cut on the
Fig. 42. A Special Fixture for Cutting Oil Grooves in the
Equalizing Gear Bushing- Interesting tool shown in Fig. 42. This device is a modification of the principle used in attachments for slotting screws with a saw held in the speed lathe. The knurled handle shown controls three motions. By screwing it in or out the bushing is tightened or released in the jaws by which it is held. Tripping it up or down drops the bushing away from or brings it up toward the revolving cutter, while springing it to one side brings the bushing out from under the cutter where it can be removed without interference. A wire finger locates the work with relation to the internal groove previously cut.
Assembling-
The operation of assembling the parts to make the complete mechan- ism includes some operations worthy of notice. In Fig. 43 is a case assembled with its two covers, and dropped into a cast-iron reaming stand, where it is held from revolving by the projecting pin shown, which enters one of the three holes in its periphery. A line reamer is used, giving assurance that the two bearings in each cover will be
MAKING EQUALIZING GEARS 43
true with each other. After this line reaming the covers are marked, numbered and burred so that the same parts will be reassembled together.
Studs E are next riveted to the covers, three on one side and three on the other, a hand hammer being used for this purpose. The ends of the rivets are cupped to facilitate this operation. The pinions are assembled on the studs, three on each side. The bushings are pressed
Fig. 43. Line-reaming the Pivot Holes in the Assembled Gear Cases and Covers
into the covers under the arbor press, and burred. The equalizing gears C and C" are dropped into place and the whole structure is then assembled. A square wrench inserted through the bore into the squared hole in (7, permits the gears to turn until they are all en- gaged. Three bolts and nuts G and G' are now passed through, bind- ing the whole solidly together.
It is of extreme importance in the quiet running of an automobile that the bevel gears run true. For this purpose the bevel gear seat on the outside diameter of the casing is not finish turned until it has been assembled as described. To do this, the mechanism is
44
No. 60— AUTOMOBILE CONSTRUCTION
mounted on the lathe on large centers, bearing on the countersinks in A and A'. These countersinks, being formed in the same operation with the ball bearing seats and the threads, are true with them. After this turning and facing, a jig fitting on this accurate seat is used for drilling the flange holes through which screws H pass to fasten the bevel gear to the casing.
The gear is pressed into place in its seat by a simple contrivance which illustrates the demand for conveniences created by the prem-
Fig. 44. A Convenient Fixture for Assembling the Gears on the Gear Case
ium system. On the bench in front of the workman is a cast-iron seat (Fig. 44) in which the bevel gear is placed face downward. The complete differential mechanism is then placed over the gear in a position to be forced down into it. The workman now reaches up above his head and brings down the hand-wheel, clamping screw and clamp shown, which is suspended by a counterweight so as to move freely up and down and remain stationary in any position. Entering the screw in the n-ut in the base of the device and turning the hand- wheel, forces the casing down into the gear and thus completes the
MAKING EQUALIZING GEARS
45
assembling. The tap bolts are now put in and are wired through holes drilled through their heads, to prevent them from turning. This completes the making of the equalizing gear.
A Good Tapping- Record
While the making of the bevel gear has not been described, it will not do to pass over one of the operations met with. This is the opera- tion of tapping the holes by which the gear is held to the flange. These holes are 5-16 inch in diameter and 13-16 inch deep and are
Fig- 45. A Tapping Operation and Operator with a Remarkable Record— 75,OOO Blind 5-16-inch Holes in Chrome-nickel Steel without breaking a Tap
blind, being tapped to a bottom and not through. The tapping is done in a Cincinnati drill press (Fig. 45), using an Errington friction chuck. Tapping in chrome-nickel steel by power is, it will be agreed, no "fool of a job." One of the difficulties met with is the tendency of the metal to seize the tap and break it when backing out.
The operator shown broke many taps in becoming familiar with his job, but since he has gotten into the swing of it, he has tapped 75,000 of these blind holes in chrome-nickel steel without breaking a tap.
46
No. 60— AUTOMOBILE CONSTRUCTION
The credit of this record must be divided between the man, the ma- chine, the chuck and the tap, but there is enough to make a respectable showing for all four. The operator's increase of efficiency was obtained with practically no change in the tools or methods, being due simply to the training of his judgment in the feeling of the tap, and in the use of excellent tools. It might be said that a firm of the highest
Fig. 46. A Completed Equalizing: Gear Set up for Testing to Destruction
Fig. 47. Condition of Shafts Broken in Tests shown In Fig. 46 ; the Gears were Uninjured
reputation for accuracy and for skill in manufacturing had asked ten cents a hole for the job. This operator runs two taps in each of the twelve holes in a gear, twenty-four holes in all, in from 15 to IS minutes.
Tests on the Finished Casing-s
Of course, the object that was aimed at in designing these equaliz- ing gears for sale to manufacturers of automobiles, was to give them such strength that some other part of the machine would break first. In order to find out whether or no this result had been obtained a
MAKING EQUALIZING GEARS 47
number of tests were made in the laboratory of the engineering school of Brown University. In Fig. 46 the casing is shown as mounted in brackets for a torsion test, the power being applied through 1-inch, 3% per cent nickel-steel shafts, specially treated. These failed at 20,300 inch-pounds, twisting through 800 degrees before rupture. Sam- ples of broken shafts are shown in Pig. 47, and give some idea, in combination with the figures just given, of the excellence of the ma- terial used in these shafts. No damage of any kind was found inside the gear casing, the mechanism being unbroken and running as easily and smoothly as before.
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UNIVERSITY OF CALIFORNIA LIBRARY
CONTENTS OF DATA SHEET BOOKS
No. 1. Screw Threads.- r i i t . d States, WhltWOPth, Sharp \"- and llritish Associa- tion Standard rriir«-ads; llriuus Pipe Thread: oil Well Casing (Safes' Kin- Hose Com Thread: Worm
Threads; Metric Threads: I'M .tch ine. Wood, and La.u rim-ads; Carriage Bolt
Threads, etc.
No. 2. Screws, Bolts and Nuts. — ril- lister-head. Square-head. Headless. Col- and Hexagon-head Screws; Stand- aru and Special Nuts; T-: <;<s, T-bolts and Washers; Tliumb Screws aid Nuts; A. L. A. M. Standard Se]v\vs and Nuts; Maehine Screw Heads; AYood Screws; Tap Drills; Lock Nt.ts; Kye-bolts, etc,
No. 3. Taps and Dies. — Hand, Machine,
Tapper and Maehine Screw Taps; Taper
dcrs Hobs; Screw Machine
'laps; Strai^lit and Taper ];oil?r Taps;
-iMilt. Wa. iiout. and 1'ateh-bolt Taps;
i Hobs; S'llid Square, Round
Adjustable and Sp.'in;- S' AV Threading
^9. 4, Rc-uners Sockets, Drills and Viir.ng Butters. — . and Reamers: Shell 1; auu-r 'ind Arbo"; ; Pipe Reamers; Taper 1 us Ream \vn & Sharpe,
M' -e a Soc'-fts and Ream-
'•r« Drills; Wire Gugos; Milling Cutters; Setung Ang-i-s for Milling Teeth in End Mills and Vngular Cutters, etc.
No. 5. t»pur Gearing*. — Diametral and
Circular Pitch; Dimensions of Spur Gears;
Tables of Pitcn Diameters; Odontograph
Tables: Rollin r Mill Gearing; Strength of
Spur Geais; liorsepo\\. mitted by
-iron and Rawhide Pinions; Design of
-t-iron Gears;
rlic < it-ai Ing.
No. 6. Bevel, Spiral and Worm Gear- ing1.— Rules and 1 .-rmulas for Bevl irength of I'.evel Cieurs; Design s; Jlules and Formulas for Spiral i- ibles Facilitating Calcu-
:-am for fitters for Spiral Ruins and Formulas for Worm Ge;
No. 7. E 'ting1, Keys and Key ways. — H"> scpow of Shafting; Diagrams and T;. les f.,r the .strength of Shafting;
'vpr« 5ng, Driving, .''hrinking and Running : Woodruff Keys; United States Navy • lard Keys: Gib Keys; Milling Key- \\avs; Duplex Keys.
TTo. 8. Bearing's, Coupling's, Clutches, Crane Chain and Hooks. — Pillow Blocks; Babbitted I'.; rings: Ball and Roller Bear- Clamp Couplings; Plate Couplings; •oupling*; Tooth Clutches; Crab nqrs; Cone Clutches; Universal ''rane Chain; Chain Friction; Crane ilool.s; Drum Scores.
No. 9. Spring's, Slides and Machine Detai;0.— Formulas and Tabl. s for Spring Calculations; M. • hine Slid<>s; Machine jIan«:-..-s ;,nd I. vets; Collars; Hand Wheels; Pins and Cotters; Turn-buckles,
No. 10. Motor Drive, Speeds and Feeds,
Change J-ear^g, and Boring1 Bars. Tower
i-erjuirod for Machine Tools; Cutting
Is and Feeds for Carbon and Iligh-
: Sie,-i: Screw' Machine Speeds and
Heat Treatment of High-speed
1 Tools; Taper Turning; Change G ing for the Lathe; Boring Bars and T
No. 11. Milling- Machine Indexing1, Clamping; Devices and Planer Jacks. —
Tables for Milling Machine. lnde\ Cha for Milling Spirals; Ai
for setting Indexing Head when Milling Clutches; Jig Clamping J and Clamps; Plant r Jacks.
No. 12. Pipe and Pipe Fittings.- pip,. Threads and Gages; Cast-iron Fiti Bronze Fittings; Pipe Flan^ Bends; Pipe Clamps anil Han.u< sions of Pipe for Various Service
No. 13. Boilers and Chimney b —Fine Spacing and Bracing for Boilers; Sin-ngth of Boiler Joints; Riveting; Boiler Setting; Chimneys.
No. 14. locomotive and Railway I>ata. — Locomotive Boilers; Beaii-g Pi -;sui -. for Locomotive Journals; L<><- »{i\< Classifications; Rail Sections; ro^s. Switches and Cross-overs; Tires; Force; Inertia of Traias; Brake Brake Rods, etc.
No. 15. Steam and Gas Engine — Sat- urated St^am; Stem Pipe Six. Kngino Design; Volume of C Stuffiing Boxes; Setting Corliss Kn Valve Gears; Condenser and Air J'unn. Data; Horsepower of Gasoline Automobile .Engine Crankshafts, otc.
No. 16. Mathematical Tables.- Squares of Mixed Number:;; Functions o J tions; Circumference and Diame :rs Circles; 'l^ables for Spacing off Circles: Solution of Triangles; Formulas f< : Solv- ing Regular Polygons; Geometric ! Pr- - gression. etc.
No. 17. Mechanics and Strength ->t Ma- terials.— Work; Energy; Centrifugal Force; Center of Gravity; Motion; Fric- tion; Pendulum; Falling Bodies; S *-engtli of Materials; Strength of Flat la Ratio of outside and Irside R ill "f Thick Cylinders, etc.
No. 18. Beam Formulas and Str^cta-.:! Design. — Beam Formulas; S- io.i-
uli of Structural Shapes; Beam .iarts Net Areas of Structural Angles Rivet Spacing; Splices for Channels .<nd I- beams; Stresses in Roof Trusses,
No. 19: Belt, Hope and Chain Drives. Dimensions of Pulleys; Weights of Pul- leys; Horsepower of Belting; Belt Veloc- ity; Angular Belt Drives; Horsepower transmitted by l:opes; Sheaves for i: Drive: Bending Stresses in Wii Sprockets for Link Chains; Formulas and Tables for Various Classes of Driving Chain.
No. 20. Wiring1 Diagrams, Heating1 and Ventilation, and Miscellaneous Tables. — Typical Motor Wiring 1 .'iagramv ance of Round Copper 'Wire; itui
: Cables; Current Densities IVr \ ous Contacts and Materials; Centrlf Fan and Blower Capacities; H,,t \v Main Capacities; Miscellaneous Tal Decimal Equivalents, Metric Conver Tables. \\'i-i^lits and Specific Gravity of IB, \Vei-his of l-'illets. Drafting i
Conventions, •
M u'TTTXEHY, the monthly mechanical journal, originator of the Reference and Data Ir'heet Furies, is puuiished in four editions — the N//o;; Kilifhm. $!.()•) a | the Engineering Edition, $2.00 a year; the Hallway Edition, $2.00 a year, and Mie Foreign Edition, $3.00 a year.
The Industrial Press, Publishers of MACHINERY, 49-55 Lafttyette Street, New York City, U. S. A.
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